1. FIELD OF THE INVENTION
The present invention relates to thermosetting resin compositions with excellent electrical properties; electrical laminates made therefrom; and methods of producing these.
2. Technology Review
Electrical laminates such as circuit boards are produced by laminating sheets of electrical conducting material onto a base substrate of insulation material. The performance of the finished circuit board is effected by the electrical characteristics of the base substrate material.
Commercially available thermoset resin systems with acceptable electrical performance at high frequencies (&gt;350 MHZ) are restricted in their applications due to high cost. The lower cost alternatives that are available do not perform satisfactorily at high frequencies due to unacceptable electrical properties, such as high dielectric constant (D.sub.k), high dissipation factor (D.sub.f), high variability of D.sub.k and D.sub.f with frequency, and consistency of D.sub.k and D.sub.f from lot to lot of production material.
Thermoplastic polymers such as polytetrafluoroethylene (PTFE) which have exceptional electrical performance at high frequencies are commercially available. The primary drawbacks associated with these materials are very high raw material costs and special processing considerations that add substantial cost to the final product. Because of the physical properties, very high laminating temperatures and pressures are also required to fabricate an electrical laminate from PTFE. Furthermore, due to the inability to "wet" PTFE, costly and hazardous chemicals are required to modify its surface during fabrication of the circuit.
A thermoset material would have much greater mechanical properties over a much broader temperature range. Additionally, since thermoset materials have better mechanical properties, this would allow the circuit board fabricator to use conventional cost effective processes.
A need exists for thermosetting resin compositions, and electrical laminates made therefrom, of low to moderate cost with acceptable electrical properties at frequencies up to at least 20 GHz. Such compositions would have great utility as circuit board substrates and the laminates made from these thermosetting resins can be utilized in many applications such as in the rapidly growing wireless communication market, in high speed computers, in high definition televisions, and in various other electrical and related applications.